Version 1.3.2 of the Icaros Desktop is now available. Icaros Desktop is one of the prime AROS distributions, ready to be used on your desktop today - no fancy PowerPC hardware required (like with AmigaOS or MorphOS). If I can get this running, it might be about time we took a closer look at this, don't you think? Thoughts?

I can understand that adds some complexity to the OS design. But then the problem is then code complexity, not performance overhead from memory protection (which is practically a non-issue in most modern architectures).

But then it is not my project. So whatever it is they want to do, it is their pregogative.

So this is what I meant. You need to set access attributes to memory allocations (pages) in a hierarchical way to keep controlled access of different layers of OS to your exposed data. If data is not exposed, it is solely belongs to an app.
Also, page size is 4KB min, so memory blocks (like messages, taglists, IO requests, shared data) need to be sorted and merged by their access rights.
Almost no chance of getting this without software modification.